The Zipper-Rift model is one explanation for the formation of this material during one part of the Earth's
 history. Nye's equation gives the profile of aggregates of it. A tuya is a volcano underneath this. According
 to one hypothesis, the largest amount of this substance present on Earth was during part of the
 Neoproterozoic era. Since this has a high albedo, feedback loops involving this and reflected light are
 important in climate models. Information about past climates can be gleaned from trapped gases and pollen
 in cores of this. The last greatest extent of this material was about 20
The Zipper-Rift model is one explanation for the formation of this material during one part of the Earth's
 history. Nye's equation gives the profile of aggregates of it. A tuya is a volcano underneath this. According
 to one hypothesis, the largest amount of this substance present on Earth was during part of the
 Neoproterozoic era. Since this has a high albedo, feedback loops involving this and reflected light are
 important in climate models. Information about past climates can be gleaned from trapped gases and pollen
 in cores of this. The last greatest extent of this material was about 20,000 years ago. For 10 points, name
 this material that makes up glaciers.
The Zipper-Rift model is one explanation for the formation of this material during one part of the Earth's
 history.
{ice} [or {frozen water}]